Research Article, J Sleep Disord Treat Care Vol: 6 Issue: 2
Positive Psychological Traits, Perceived Stress and Quality of Life Associated with Sleep Quality in Community-Dwelling People
*Corresponding Author : Shu Ping Chuang
Department of Psychiatry, Zuoying Branch of Kaohsiung Armed Forces General Hospital No. 553, Jiunshiau Rd., Zuoying District, Kaohsiung 81342, Taiwan
Received: July 30, 2015 Accepted: January 02, 2017 Published: May 09, 2017
Citation: Chuang SP, Wu JYW, Wang CS, Pan LH (2017) Positive Psychological Traits, Perceived Stress and Quality of Life Associated with Sleep Quality in Community-Dwelling People. J Sleep Disor: Treat Care 6:2. doi: 10.4172/2325-9639.1000190
Background: The objective of this study was to identify the sleep problems most often encountered by people according to the presence or absence of physical and mental disorder. The aim of the present study was to investigate the associations among positive psychological traits, perceived stress, quality of life and sleep quality in community participants.
Methods: Three hundred and sixty-seven community participants aged 20 to 90 years old completed SHS, GQ-6, AHS, PSS, PSQI and WHOQOL-BREF. Participants with severe physical disorders, sleep disorder, and those taking psychotropic medication were excluded from the study.
Results: Stepwise regression analysis was applied in the analysis. Happiness, hope, perceived stress and quality of life were associated with sleep quality. Gratitude showed no significance. Happiness, hope, perceived stress and quality of life explained 31% of the variance for sleep quality. A majority of participants (73.5%) had PSQI ≥ 5, which is suggestive of sleep problems. The poor sleep group had lower scores on positive psychological traits (except for gratitude), higher perceived stress and lower quality of life compared to the good sleep group.
Conclusions: Our results suggested that preventive and intervention programs targeting community participants should focus on developing strategies to increase positive psychological traits and decrease perceived stress in order to improve sleep problems.
Keywords: Positive psychological traits; Happiness; Gratitude; Hope; Perceived stress; Sleep quality; Quality of life
Sleep disturbance is a widespread problem and a common complaint among different populations and age groups [1-3]. Worldwide, one quarter to one third of adults experience complaints of disturbed sleep [4,5]. Numerous studies suggested that sleep problems are associated with chronic illnesses and reduced mental health and may affect both quality of life and productivity [6-9]. Thus, it is imperative to investigate the factors associated with sleep problems in order to understand the complex process it may have on the impact of mental health.
Positive psychology has emphasized the importance on the positive aspects of life [10-12] and positive traits have been shown to have impact on health and well-being [13-15]. Previous research suggested that gratitude was correlated to better sleep quality [16,17]. In addition, Mccullough et al.  found that gratitude was correlated with other measures of positive traits, such as vitality, happiness, satisfaction with life and hope. In a community-based study, women with a higher level of marital happiness experienced fewer sleep disturbances , and a greater happiness was also found in association with better sleep conditions among older participants . Based on results of previous studies, we hypothesized that one’s subjective and positive internal feelings have a greater direct impact on sleep quality. This study examined these questions with regard to the specific positive psychological traits of happiness, hope and gratitude.
Stress is thought to be an important factor that influences an individual’s sleep-related complaints and physical health, suggesting that personal variations in stress reactivity determines the degree to which stress may decrease the level of mental health [20-24]. Individuals with a higher level of perceived stress displayed greater sleep disturbances and experience an increased cardiovascular risk profile between the ages of 50 and 60 compared to those with a lower level of perceived stress . Previous findings have shown that increased perceived stress was strongly associated with sleep disturbances [26-29]. McHugh et al.  found that perceived stress mediated the relationship between emotional loneliness and sleep quality in older adults. Thus, the level of perceived stress may have a big impact on a person’s sleep disturbances, which may cause people to feel hyper-aroused and reduce sleep quality. Specifically, studies have shown that sleep disturbances are associated with the reduced perception of overall quality of life among people with physical and mental disorders [31-33]. It is important to understand if sleep disturbances influence the quality of life in the general population. Given the increased understanding of poor sleep in community residents, it is crucial to gain a better understanding of sleep quality and its relationship with positive psychological traits, perceived stress and quality of life.
We hypothesized that individuals in the poor sleep group would show lower scores in positive psychological traits and quality of life, higher perceived stress when compared to the good sleep group. In addition, we will also attempt to identify correlates of sleep quality from sociodemographic variables, positive psychological traits, perceived stress and quality of life.
The study protocol was reviewed and approved by Kaohsiung Armed Forces General Hospital institutional review board. The sample was recruited in Kaohsiung city and participants were randomly selected from the community through advertisements in the Internet, hospital and community bulletin board. Questionnaires were sent to participants left their address and telephone numbers, and agreed to participate in the study (total 507 participants). Fortythree participants had missing data (the participants with missing information on questionnaires) and 56 failed to send back their questionnaires and refused to attend the study. We also excluded 24 individuals with severe physical illness (such as sleep disorder, stroke, cancer and nervous system disease) and 17 who were receiving psychiatric medicine. In total, 367 questionnaires were completed, with a response rate of 80.4%. All participants gave written consent to participate in the study.
Subjective happiness scale (SHS): The SHS is a 4-item scale of global subjective happiness. Two items describe a person’s mood and ask respondents to consider how similar the description portrays themselves on a 1 to 7 scale (1 = "not at all", 7 = "a great deal"), whereas the other two items give brief descriptions of happy and unhappy individuals and ask respondents the degree to which each description characterize them . The Chinese version of SHS was indicated to have good reliability and validity .
Gratitude questionnaire - 6 (GQ-6): The GQ-6 is a 6-item selfreport measure of gratitude. Respondents are asked to report their experience of gratitude on a 1 to 7 scale (1 = "strongly disagree", 7 = "strongly agree"). The GQ-6 has good internal reliability, with alphas between .82 and .87 , and the Chinese version of GQ-6 demonstrates good reliability and construct validity .
Adult hope scale (AHS): The adult hope scale (AHS) measures the cognitive model of hope including two constructs, (a) agency (goal-directed energy), and (b) pathways (planning to meet goals). The AHS comprises of 12 items, including four items that measure the pathways for thinking, four items that measure the agency for thinking, and four filler items. Respondents are asked to answer each item using an 8-point scale ranging from definitely false to definitely true . The Chinese version of AHS was used in this study and showed good reliability and validity .
The perceived stress scale (PSS): The PSS is 14-item questionnaire which instructs respondents to appraise certain experiences of perceived stress in the preceding month, each with a possible answer rated on a five point Liker-type scale (from 0 = never to 4 = very often). Total scores are calculated after reversing positive items’ scores and then summing up all scores. The range of possible scores is 0-56 with higher scores indicating greater stress . The Chinese version of PSS was used in this study .
The Pittsburgh sleep quality index (PSQI): The Pittsburgh Sleep Quality Index (PSQI) is an effective instrument used to measure sleep quality and disturbances in the last month. It examines seven areas: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction over the last month. Respondents were asked to answer each item based on a 0 to 3 scale; 3 indicates a negatively extreme response. A global score of above 5 indicates a poor sleeper . The Chinese version of PSQI was used in this study .
Quality of Life (WHOQOL-BREF Taiwan version): There are four subscales in the WHOQOL-BRIEF Taiwan Version: physical health (including level of independence), psychological state (including personal beliefs), social relations, and relationship to salient features of the environment. All items were rated on a 5-point scale with higher scores indicating a higher quality of life. WHOQOLBREF Taiwan Version has been found to have good internal reliability and validity .
Data analysis was carried out using SPSS22.0. Comparisons of test results between genders and poor sleep group and good sleep group were performed using two sample t-tests and chi-square statistics as appropriate. Bivariate statistics using Spearman correlation were generated to understand the inter-relationship between the constructs. Stepwise regression analyses were used to explore which variables remained significant predictors of sleep quality. An alpha level of 0.05 was applied.
Characteristics of participants
Table 1 illustrated the demographics as follows: the mean age of men and women were 41.3 years (SD =13.8 years) and 46.0 years (SD =13.6 years), respectively. A majority of participants had a education level of senior high school and above (73.5%), 68.9% were married, 65.6% were employed, and 18.8% were retired, 7.9% diabetics, and 9.2% with hypertension. There were no significant differences between men and women in all clinical characteristics. A majority of participants (73.5%) had PSQI ≥ 5, which is suggestive of poor sleep quality.
|Measure||Men (n=136) Mean (SD) /n (%)||Women (n=231) P Mean (SD)/n (%)|
|Age (years)||41.3 ± 13.8||46.0 ± 13.6 0.002**|
|Currently employed||114 (83.8 %)||127 (54.9 %)|
|Retired||22 (16.2)||47 (20.3%)|
|Housewife||0 (0%)||57 (24.8%)|
|Single||45 (33.0%)||39 (16.8%)|
|Married||89 (65.4%)||164 (70.9%)|
|Others||2 (1.6%)||28 (12.3%)|
|Master’s degree||17 (12.5%)||15 (6.5 %)|
|University||65 (47.7 %)||89 (38.5 %)|
|Senior high school||41 (30.1%)||75 (32.5 %)|
|Junior high school||10 (7.3 %)||28 (12.1 %)|
|Elementary school||3 (2.4%)||24 (10.4 %)|
|Current smoker||26 (19.1 %)||5 (2.1 %) .000***|
|35 (25.7 %)||13 (5.6 %) .000***|
(once or twice a week or daily)
|56 (41.1 %)||114 (49.3 %) .264|
|Volunteering||13 (9.5 %)||43 (18.6 %) .005**|
Table 1: Characteristics of study participants.
Comparisons between the poor sleep group and the good sleep group showed significant differences in all clinical variables, including all domains of sleep quality and quality of life, except for gratitude (Table 2).
|Measure||Poor sleep group (n=270)||Good sleep group (n=97)||P|
|M (SD)||Median||M (SD) Median|
|Subjective Happiness Scale (SHS)||19.4 (3.5)||19.0||21.5 (4.0) 22.0||.000***|
|Gratitude Questionnaire-6 (GQ-6)||30.91 (4.4)||31.5||30.61 (5.5) 31.0||.597|
|Adult Hope Scale (AHS)||46.4 (7.4)||47.0||50.48 (6.8) 51.0||.000***|
|The Perceived Stress Scale (PSS)||24.6 (7.0)||25.0||17.8 (7.3) 17.0||.000***|
|The Pittsburgh Sleep Quality Index (PSQI)||9.6 (2.9)||9.0||3.7 (1.2) 4.0||.000***|
|Subjective sleep quality||1.3 (0.7)||1.0||0.5 (0.5) 1.0||.000***|
|Sleep latency||2.3 (1.4)||2.0||0.6 (0.8) 0.0||.000***|
|Sleep duration||1.2 (0.8)||1.0||0.6 (0.7) 0.0||.000***|
|Habitual sleep efficiency||2.2 (1.1)||3.0||1.2 (1.3) 1.0||.000***|
|Sleep disturbances||1.4 (0.5)||1.0||0.8 (0.5) 1.0||.000***|
|Daytime dysfunction||1.3 (1.1)||1.0||0.1 (0.4) 0.0||.000***|
|Use of sleeping medicine||0.2 (0.6)||0.0||0 (0) 0.0||.002**|
|WHOQOL-BREF Taiwan Version||55.9 (7.4)||55.4||63.5 (6.1) 63.4||.000***|
|Physical health||14.7 (2.0)||14.8||16.9 (1.6) 17.1||.000***|
|Psychological state||13.4 (2.3)||13.3||15.5 (1.9) 15.3||.000***|
|Social relations||13.8 (2.1)||14.0||15.3 (1.9) 16.0||.000***|
|Relationship to salient features of the environment||13.8 (2.0)||14.2||15.6 (1.6) 16.0||.000***|
Table 2: Means, standard deviations (SD) and median of study variables.
Correlations of happiness, gratitude, hope, perceived stress, domains of quality of life and PSQI are presented in Table 3. Age, education (years) and gender were not correlated with PSQI, but age was associated with daytime dysfunction (r=-.26, p<.001), habitual sleep efficiency (r=.11, p<.05), education associated with daytime dysfunction (r=.19, p<.001) (data not shown).
|7. subjective sleep quality||-.28**||-.07||-.25**||.46**||.57**||.32**||___|
|9. sleep disturbances||-.24**||.04||-.21**||.34**||.56**||.22**||.42**||.41**||___|
|10. daytime dysfunction||-.35**||-.08||-.29**||.49**||.67**||.16**||.40**||.31**||.28**||___|
|11. habitual sleep efficiency||.00||.00||-.00||-.00||.39**||.07||.06||.03||.08||.04||___|
|13 physical health||.40**||.14*||.40**||-.58**||-.56**||-.25**||-.55**||-.42**||-.41**||-.47**||-.04||.87**||___|
|14. psychological state||.49**||.15**||.51**||-.63**||-.51**||-.22**||-.46**||-.34**||-.39**||-.50**||-.02||.89**||.73**||___|
|16. relationship to salient features of the environment||.43**||.14**||.42**||-.56**||-.51**||-.25**||-.45**||-.34**||-.41**||-.46**||-.06||.90**||.76**||.75**||.70**||___|
Table 3: Correlations among sleep quality (n=367).
The aim of the present study was to understand the extent to which sociademographic variables, positive psychological traits, perceived stress and quality of life were independently related to sleep quality. Four stepwise multiple regression analyses were performed, as shown in Table 4, allowing significant variables that are related to the dependent variables to enter the assessment to predict sleep.
As summarized in Table 4, happiness, hope, perceived stress and quality of life emerged to contribute significantly as predictors of subjects’ sleep quality (adjusted R2=.31, p<.001). Sociodemographic variables and gratitude were not significant contributors (data not shown). Table 4 presents the details of beta weights of each contributing variable.
Table 4: Multiple regressions predicting sleep quality from sociodemographic variables, positive psychological traits, perceived stress and quality of life (n=367).
The present study is one of the first to empirically examine the relationship among positive psychological traits, perceived stress and quality of life and sleep quality in community residents. The poor sleep group reported lower scores on positive psychological traits, except for gratitude, on domains of quality of life, higher scores on perceived stress and domains of sleep quality than the good sleep group. It appeared that people with good sleep conditions have more positive traits (happiness and hope), less stress level and better quality of life. Happiness and hope were related to total sleep quality, suggesting that having more positive feelings may have a greater impact on one’s sleep quality. Other researches have similar results that found greater happiness to be associated with better sleep conditions [18,19].
Our findings found that perceived stress was related to total sleep quality, suggesting that an increase in stress can impair the quality of sleep. Similar to previous studies, we also found that perceived stress was related to many domains of sleep disturbances [26-29]. The evidence provided by McHugh et al.  as well as our own results, suggested that perceived stress may have an important role on improving the repercussion of sleep disturbances.
Up to present, limited studies have investigated the role of positive psychological traits among adults free of physical illness, psychotropic medication or sleep disorder. In this study, we measured gratitude; however, inconsistent with previous literature [15-17], gratitude was not related to total PSQI (including domains of sleep quality). Wood et al.  showed gratitude to be correlated with domains of sleep disturbances in young adults. Emmons et al.  randomly divided people with neuromuscular disorders into the gratitude condition or control condition (hassles and neutral life events or social comparison), and found that the gratitude group reported increased hours of sleep and refreshment on waking compared with the control group. Among university students, increased levels of gratitude have also shown higher levels of perceived social support and lower levels of stress and depression . This discrepancy may be due to the fundamental dimensions of gratitude as a cognitive and emotional reaction, involving a life orientation towards what one has received . Lazarus et al.  noted that gratitude has been called an empathic emotion, which requires the recognition to how one may benefit from the actions of other people. In other words, gratitude requires more awareness of appreciation towards the world than mainly focusing on subjective well-being or mood. Another probability for the inconsistency may result from the characteristics of the participants. The participants in the present study were middleaged and employed, indicating the importance of their role and duty to take care of the family and need to deal with work-related stress during this current stage in life. Under stress, the fluctuation of emotions may be more readily activated, hindering one’s ability to appreciate the environment and or those around them. Gratitude was not associated with total and domains of sleep quality in the regression model, which remained an impact on total and domains of quality of life. Our results also found that sleep disturbances were negatively correlated to quality of life, indicating that poor sleep quality reduced one’s quality of life among community participants. Several studies showed that patients with chronic obstructive pulmonary disease (COPD) had more sleep disturbances and were more likely to have lower health-related or disease-specific quality of life [46,47]. A crosssectional study on extremely obese patients indicated that poor sleep was, as predicted, strongly associated with poor quality of life .
Limitations and Conclusion
This study had several limitations. First, the cross-sectional nature of our study did not allow us to test the causal effect of positive psychological traits, perceived stress and quality of life with sleep disturbances in community subjects. Second, by using community participants, caution should be made when trying to infer the study results to clinical samples, especially those diagnosed with sleep disorder. Thus, future studies need to probe whether the findings can extend to clinical samples, perhaps using the experimental methodology. Third, participants in this study were recruited through advertisements in Kaohsiung city, which may attract people with less stress and a more positive attitude. A larger and more representative sample of community dwelling adults is needed in future studies in order to compare different age groups and to verify the investigated variables. Finally, although this study provides a comprehensive model for understanding the association with positive psychological traits, perceived stress, quality of life and the sleep quality in community participants, it allows only a tentative glance into its explanatory mechanisms. The community sample had the advantage of a wide range of both positive psychological traits, perceived stress, quality of life and sleep quality, whereas a slanted clinical sample would probably have expressed range restrictions, producing biased statistical analysis. Furthermore, the PSQI was rated on self-report measures; thus, further research is needed into whether positive psychological traits, perceived stress, quality of life are related to objective sleep quality measured by EEG, actigraphy and polysomnography. Prospective longitudinal study designs are required to replicate findings.
The results present the first indication that individual differences in positive psychological traits, perceived stress and quality of life are related to sleep problems. Given the impact of subjective happiness, hope, perceived stress and quality of life on sleep, increasing importance should be placed on developing effective training or intervention on the improvement of sleep disturbances. Coote et al.  provided a self-help and positive goal-focused intervention to effectively increase one’s psychological well-being and decrease one’s depressive symptoms. The intervention focused on teaching goal setting and planning (GAP) skills. Empirical findings were used to further extend this program to target on the importance of selfconcordance (self-concordant goals allow people to pursue for interest or enjoyment rather than being controlled by external forces) [50,51]. Other results showed that stress management techniques improve sleep problems . Gaining a positive psychological perceptive to sleep could provide a better understanding towards the mechanism and explanation on sleep disturbances. More research is needed to examine the role of happiness, hope, perceived stress and quality of life in relation to sleep quality in both healthy and clinical populations.
This study was supported by grant from Zuoying Branch of Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan (ZAFGH102-21).
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